Rubber Hardening
As temperature falls, an elastomer generally becomes stiffer and less able to conform to changes in the sealing surfaces. A seal that works at room temperature may respond too slowly during cold operation.
BY MATERIAL
GLT O-Rings
FLUID manufactures custom GLT O-rings using genuine Viton™ GLT-series fluoroelastomer materials.
FLUID combines custom O-ring manufacturing with material selection and seal design support for new requirements and existing sealing issues.
Start with your drawing, existing O-ring specification or sealing problem. The proposed compound, material documentation and supply requirements are confirmed for each project.
Request a Technical Review
Initial response within 12 hours.
01 / GLT REQUIREMENTS
Why Choose GLT Instead of Conventional FKM?
A conventional FKM compound may provide suitable fluid resistance but insufficient flexibility or recovery for a particular cold-start or low-temperature sealing requirement.
GLT-series materials offer specialized low-temperature options within the FKM family. An appropriately formulated compound may retain useful flexibility and recovery at temperatures where some conventional FKM compounds become less responsive.
This can be valuable when a seal must maintain contact during cooling, restart after a cold soak or respond to movement and pressure changes. However, improved low-temperature flexibility alone does not establish suitability. The selected compound must also meet the application's media, compression, pressure and operating requirements.
GLT is a material selection option, rather than a universal replacement for conventional FKM.
02 / GLT REQUIREMENTS
Why O-Rings Can Leak at Low Temperatures
An O-ring can leak in cold service without visible cracks or other obvious damage. Several effects may act together.
Thermal Contraction
The O-ring and its surrounding hardware contract as they cool, often by different amounts. Depending on the gland geometry and tolerances, this can reduce effective squeeze or create a loss of contact.
Elastic Recovery
After deformation or movement, a cold O-ring may recover more slowly. This matters when the seal must follow a moving surface, accommodate a changing clearance or re-establish contact after a pressure change.
Contact Sealing Force
Sealing depends on maintaining adequate contact with the mating surfaces. Compound stiffness, installed squeeze, thermal contraction and previous compression history all affect that contact. A ring can remain physically intact while no longer maintaining an effective seal.
Low-Pressure Sealing
System pressure can help energise a correctly installed O-ring. During cold startup, standby or low-pressure operation, this assistance may be limited, making initial squeeze and material recovery particularly important.
GLT may help address the material side of these problems, but groove design, tolerances and the operating sequence still require review.
03 / GLT REQUIREMENTS
Understanding TR-10
TR-10 is a temperature-retraction measurement used to assess the low-temperature behaviour of vulcanised rubber.
In the test, a specimen is stretched and cooled while held in an extended condition. It is then released and warmed under controlled conditions. TR-10 is the temperature at which the specimen has recovered 10% of the imposed extension.
ASTM D1329 describes the temperature-retraction method. Its results help engineers compare the recovery behaviour of compounds and assess their potential for cold-service applications.
TR-10 is not the minimum operating temperature of a finished O-ring.
It does not reproduce the complete seal assembly, gland tolerances, pressure, media exposure, movement or service history. Static and dynamic seals may also respond differently to the same compound.
A published TR-10 value should therefore be reviewed with its compound identity and test conditions. It should not be converted into a sealing-temperature guarantee by applying a fixed temperature allowance.
For a broader explanation of temperature retraction and low-temperature brittleness testing, explore our Low-Temperature O-Rings application guidance.
04 / GLT REQUIREMENTS
Temperature and Chemical Compatibility
Low-temperature FKM compounds can differ in fluid resistance, even when their cold flexibility is comparable. The proposed compound should be evaluated against the actual media and the full operating temperature cycle.
GLT should not be selected solely because an application operates in the cold. Fuels, oils, additives, cleaning agents and chemical mixtures can affect swelling, shrinkage, hardness and mechanical properties. These changes may alter the seal's squeeze, recovery and resistance to damage.
Assess the full operating cycle, including cold startup, normal running temperature, shutdown and cleaning exposure. Room-temperature immersion data may not represent prolonged service, changing temperatures or a different fluid formulation.
Different low-temperature FKM compounds are not automatically interchangeable. Where a particular material or compound is specified, confirm its identity, relevant properties and availability for the project.
05 / GLT REQUIREMENTS
Low-Temperature Seal Design
Selecting GLT does not remove the need for an appropriate seal design. Review the following factors together.
Squeeze and Groove Geometry
Installed squeeze creates the initial sealing contact. Groove depth, cross-section tolerances, stretch and the dimensions of the mating parts determine how much compression is actually available.
Review the tolerance extremes at the cold operating condition. Simply increasing squeeze is not a universal solution: excessive compression can increase assembly force, friction and damage risk.
Gland Fill
The groove needs sufficient space to accommodate the O-ring throughout the operating cycle. Evaluate thermal expansion, fluid-induced volume changes and dimensional tolerances as well as cold contraction.
A design that works at the minimum temperature must also remain suitable when the equipment warms up.
Compression Set and Recovery
An O-ring's ability to recover can change after prolonged compression, thermal exposure or fluid contact. Previous service at higher temperatures may affect its subsequent cold-start behaviour.
Compression set measures residual deformation under specified test conditions. It is relevant to material review, but it is not a direct measurement of remaining sealing force or service life.
Pressure and Extrusion Gap
Consider minimum pressure as well as normal operating pressure, peaks and pressure reversals. Low-pressure sealing depends strongly on initial contact, while higher pressure can introduce extrusion risks.
The clearance between mating parts must be assessed with compound properties, temperature, tolerances and hardware movement. Back-up support may be required where the application presents an extrusion risk.
Static and Dynamic Sealing
Static seals must maintain contact as the assembly cools and warms. Dynamic seals must additionally accommodate movement, friction, lubrication and surface wear.
Cold starting conditions can differ significantly from steady operation. A compound that is suitable for a static joint should not automatically be assumed suitable for a reciprocating or rotating seal.
Temperature Cycling
Repeated heating and cooling can change dimensions, contact conditions and material response. Review cycle frequency, dwell time, cooling rate and whether pressure or movement begins before the assembly has warmed.
The complete operating sequence is often more useful than a single minimum-temperature figure.
06 / GLT REQUIREMENTS
Material Selection Considerations
Customers do not need to specify a raw-polymer grade to begin a GLT O-ring enquiry. A drawing, existing material specification or clear description of the application provides a practical starting point.
The final compound's performance depends on more than the brand material name. Formulation, hardness, cure condition and finished-part quality can influence recovery, compression set and fluid compatibility.
FLUID reviews the proposed material and available supporting information against the application. Specific material grades, compound details, source documentation and supply conditions are confirmed for each project. Documentation requirements should be agreed before ordering.
Published polymer or reference-compound properties should not be treated as guaranteed performance of the finished O-ring. Where a requirement is critical, the necessary compound evidence and application validation should be defined.
For broader material selection, explore our FKM O-Rings overview. For comparisons across different low-temperature elastomers, see our Low-Temperature O-Rings application page.
07 / REVIEW
Share Your GLT O-Ring Requirements
To help us review the requirement, share the information available. You do not need a complete specification to start. Tell us what is known and which conditions still need clarification.
- 01
O-ring dimensions, drawing and dimensional tolerances.
- 02
Existing material, hardness or compound specification, if known.
- 03
Minimum operating temperature and cold-start temperature.
- 04
Normal temperature, short-term peaks and exposure duration.
- 05
Heating and cooling cycles, including cold-soak periods.
- 06
Media, concentration, additives and cleaning exposure.
- 07
Minimum, normal and maximum pressure, including pressure reversals.
- 08
Static or dynamic operation, with movement and lubrication details.
- 09
Groove dimensions, mating materials, clearances and surface conditions.
- 10
Previous leakage, damage or replacement history.
- 11
Required quantity and material or inspection documentation.
08 / RELATED PATHS
Continue the technical discussion
09 / TECHNICAL REVIEW FAQ
GLT O-Ring FAQ
Is GLT the same as standard FKM?
GLT belongs within the FKM material family but identifies a specialized low-temperature material option. Conventional FKM compounds vary widely, so suitability should be compared using the proposed compounds and actual operating conditions, rather than the material names alone.
Does TR-10 tell me the lowest temperature at which an O-ring will seal?
No. TR-10 describes recovery in a controlled material test. Finished-seal behaviour also depends on squeeze, gland tolerances, pressure, media, movement and service history. It is a useful selection input, rather than a standalone operating limit.
Why can an O-ring leak during cold startup but seal after warming?
Cooling can increase stiffness, slow recovery and change contact through thermal contraction. Low startup pressure may provide limited pressure energisation. Warming can improve material response and change the assembly dimensions, but the cause should be investigated rather than assumed from this symptom alone.
Can I replace an existing FKM O-ring with GLT without changing the groove?
Possibly, but the replacement requires review. Confirm dimensions, hardness, media compatibility, squeeze, gland fill and operating conditions. A different compound may affect assembly force, recovery, friction and extrusion behaviour even when the nominal O-ring size is unchanged.
Can GLT O-rings be used in dynamic applications?
Selected dynamic applications may be suitable following compound and design review. Movement, speed, pressure, surface condition, lubrication, wear and cold-start behaviour must be considered. Suitability for a static seal does not establish suitability for every dynamic application.
NEXT STEP
Discuss Your GLT O-Ring Requirement
Share your drawing, operating conditions or existing sealing problem. FLUID will review the available information and help clarify the material, design and documentation requirements for supply evaluation.
Request a Technical Review
Initial response within 12 hours.
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